Tack pins are relatively new and are widely used in the field of consumer electronics. Tack pins are generally very small, for example, having a shank diameter of around 1.0 mm. Their miniature size and ability to provide a reliable attachment force has generally replaced screws.
Tack pins connect overlapping panels by permanently deforming the panel material surrounding the hole in which the tack pin is installed. During installation, the shoulder on the tack pin shank, which has a diameter larger than the lower panel hole diameter, vertically compresses (deforms) and forces lower panel material into an undercut in the shank. The lower panel material firmly clinches the shank at the undercut and locks the tack pin in place.
For improved attachment, compression installed fasteners such as a miniature tack pins should preferably apply a residual clamp load to the attached panels. Typically, the head of a tack pin is flat and extends generally perpendicularly to the longitudinal axis of the shank. Because the head is flat, it does not elastically deform during installation to provide a residual clamp load on the panels. It has been proposed to provide a tack pin with an enlarged head having the desired resilience characteristics. However, since tack pins must be significantly harder than the materials to which they attach, providing a tack pin head with the desired resilience is difficult to achieve. For example, joining a fastener head composed of one material to a shank composed of a second material requires an extra manufacturing step. Furthermore, the shanks are very small and very difficult to physically handle. Therefore, it would be desirable to provide a tack pin with resilience features that apply a residual clamp load to the attached panels after installation.
U.S. provisional patent application No. 62/113,846 entitled “Assembled Clamp Tack” discloses a fastener formation process in which separate components are joined simultaneously with formation of the main body of the fastener. More specifically, a head element is joined to the shank while the shank features are formed from a blank. The manufacturing process is carried out by a punch-and-die combination in a single pressing stroke. While this preassembly step solves the problem of handling miniature parts when the head and shank comprise separate components, it still requires an assembly step. Therefore, it would be desirable to provide a tack pin that applies a residual clamp load to the attached panels after installation but does not require the step of assembling separate head and shank components.